Denton County is reporting its first human case of West Nile this year: a man in his 40s diagnosed with what officials say is a mild case of the fever. It's one of the rare human cases of West Nile reported this summer, a far cry from the deadly outbreak of 2012.

"We still have people who may be contacting their physicians or the county reporting that they might be ill from this parasite," Thompson said Thursday. Despite the fact the number is relatively low, just double the eight initially reported on July 16, "I don't think we can relax," says Thompson. "People are hearing more and more about it, and then they call and say they think they have the parasite."

As of today the Centers for Disease Control and Prevention is reporting 66 cases in the state -- third only to Iowa (with 138 cases) and Nebraska (with 70), where cases began appearing in late June. A handful of other states, from Wisconsin to Georgia, are reporting one or two cases. (Texas health officials actually county 80 statewide.)

Folks with cyclosporiasis, which is usually brought on by ingesting water or food contaminated with feces, won't show symptoms for two to 14 days. But when they do, they're potent: "explosive diarrhea," per the Mayo Clinic. And that lapse between ingesting the parasite and actually getting sick is the main reason health officials are having problems identifying the source of the infection.

"When people get sick, they don't go to the doctor immediately," says Belen Moran, spokesperson for the CDC, which is working with health officials in Texas and elsewhere to track the source of the infection. "And when they do and when they're tested, it takes a few days to get those results back. And if they do have the parasite, an epidemiologist will ask them what they ate three weeks ago. So it can be very hard to pinpoint. ... We just don't know if the cases are linked."

Or if they're spreading: According to the Texas Department of State Health Services, there are 15 cases in Collin County, 13 in Denton County and a handful in more than a dozen others. Denton County, says county health spokesperson Sarah McKinney, is "holding strong at eight cases, and we're hoping we're seeing the tail end of this." But, she says, people are still calling every day asking if they're infected. It's hard to say unless they go to the doctor, who can diagnose the parasite -- and prescribe an antibiotic that will tend to the bug.

"It's not something that gets better on its own," says McKinney.

"All we can do," says the CDC's Moran, is "simply remind people what to do: Clean your fruit and vegetables, and if you're feeling sick go to the doctor. This is not a fatal disease, but it can last months."